1. Field
This disclosure generally relates to aircraft structures, and deals more particularly with a bonded composite wing.
2. Background
Fiber-reinforced resins, commonly referred to as “composites”, are being used more frequently in the aerospace structures because of their relatively high strength-to-weight ratios, good corrosion resistance, and other beneficial properties. Conventional composites used in aerospace applications include glass, carbon, or polyaramid fibers in woven and non-woven configurations, held in a resin matrix resin such as epoxy. Plies of the composite are laid up over tools and then cured through application of a combination of heat and pressure to form a hardened laminate. In some cases, a core material such as a foam or a honeycomb is placed between the plies to form a composite sandwich.
In large commercial aircraft, composites are frequently employed in secondary structures but their use has been limited in primary structures such as wings which are manufactured predominantly from metals such as aluminum, titanium, etc. For example, some recent aircraft have used composite wing skins that are attached to metal structural spars and chords with metal fasteners. The metal fasteners add undesired weight to the aircraft and are subject to corrosion. Current wing designs also have other disadvantages. For example, current wings are not easily tailored to optimize a combination of flight characteristics such as lift, stiffness, bending, torsion, and discrete damage containment/arrestment. Additionally, current wing designs may employ many spars and/or chords that are heavier than desired, or which may not be optimized to transfer loads from the wing skins.
Accordingly, there is a need for a composite wing structure that substantially eliminates the need for metal fasteners and which exhibits improved discrete damage containment. There is also a need for an all-bonded composite wing structure having upper and lower composite skins of differing interlaminar fracture toughnesses and stiffness that are tailored to optimize flight characteristics, service life durability and fail-safe reliability.